1. Field of the Invention
The present invention relates to an electric contact device that electrically connects a camera body to a replaceable lens unit, a lens unit that includes an electric contact device, and an imaging device.
2. Description Related to the Prior Art
A digital camera which includes a camera body and a lens unit and of which the lens unit can be replaced has been applied. The camera body is provided with an imaging element and a control circuit board for controlling each part such as the imaging element, and a lens mount on which the lens unit is mounted is provided on the front surface thereof. The lens unit is a unit in which lenses, a diaphragm, an optical filter, and the like are integrated.
Further, a digital camera, which automatically adjusts exposure or performs focusing, has been applied in recent years. In a digital camera that performs automatic exposure control and automatic focusing, a control circuit board is provided not only in a camera body but also in a lens unit. The control circuit board of the lens unit is connected to the camera body through an electric contact device provided in a lens mount; transmits/receives control signals, which are used for the automatic exposure control and the automatic focusing, to/from the camera body; and controls the position of a lens and the aperture of a diaphragm.
For example, an electric contact device that includes a board on which a conductive pattern is formed, a contact member that is fixed to the board by being caulked to a hole formed in the board, a base that holds the contact member so as to allow the contact member to be displaced between a protruding position and a retracted position, a biasing member that biases the board in a direction in which the board comes into pressure contact with the contact member, and a support member that supports the biasing member (Japanese Patent No. 4901811) is known as an electric contact device that connects a lens unit to a camera body.
Since the biasing members are supported by only the support member in the electric contact device disclosed in Japanese Patent No. 4901811, there is a problem in that a gap is formed between the biasing member and an inner wall (a part of the base) of the electric contact device adjacent to the biasing member. For example, when the electric contact device disclosed in Japanese Patent No. 4901811 is disposed in the camera body so as to be parallel to a mounting surface, a distance between the contact member and the side wall of the mounted lens unit is increased by a gap between the biasing member and the inner wall of the electric contact device. For this reason, since a lens having a small diameter should be used as a lens (particularly, a lens closest to the imaging element) used in, for example, the lens unit, the design of the lens is limited.
Further, the contact member is fixed to the board in the electric contact device disclosed in Japanese Patent No. 4901811. However, since the distance between the contact member and the side wall of the mounted lens unit is long, fixed portions are loosened due to the mounting/detachment of the lens unit on/from the lens mount, the load of the lens unit while the lens unit is mounted on the lens mount, or the like. For this reason, since connection becomes unstable with time, there is a case in which automatic exposure control and automatic focusing cannot be performed normally. Particularly, when caulking is loosened in a case in which the contact member is fixed to the board by caulking and the biasing member is supported by only the support member, the biasing member is shaken due to the gap between the biasing member and the inner wall of the base and, for example, the biasing member bends in the middle thereof. For this reason, instability is further caused.